-LRB- CNN -RRB- -- Police in Brazil say they have arrested a fourth person in connection with the March 30 rape of an American woman and the beating and robbery of her French boyfriend on a minibus in Rio de Janeiro .

The fourth person arrested -- a 13-year-old boy -- is accused of helping steal the tourists ' credit cards , police said Tuesday .

According to Brazilian media , the boy has denied involvement in the rape .

Police said the woman and man boarded the minibus in the Copacabana beach district in Rio de Janeiro early on March 30 . Three men subsequently boarded the minibus and forced off all the other passengers , police said .

The woman was raped and her boyfriend was held captive and robbed , authorities said .

Their credit cards were used at several locations inside and outside of Rio de Janeiro over a span of hours , police said .

According to Brazilian newspapers , the man was handcuffed and beaten , while the woman was repeatedly raped . The two were dumped in Itaborai , a city more than 30 miles -LRB- about 50 kilometers -RRB- away , after six hours , O Globo newspaper said .

Earlier , police arrested three other people in the case : Carlos Armando Costa dos Santos , Jonathan Foudakis de Souza and Wallace Aparecido Souza Silva .

The rape highlights security concerns in the Brazilian city that will host matches in the 2014 World Cup and will put on the Summer Olympics two years later .

As more women came forward saying they were victims of similar attacks , Rio de Janeiro Civil Police Chief Martha Rocha issued a written apology . She also fired two police officers responsible for handling rape cases .

CNN 's Shasta Darlington contributed to this report from Sao Paulo , Brazil

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A 13-year-old boy is accused of helping steal the victims ' credit cards , police say

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The boy denies involvement in rape , Brazilian media report

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The incident highlights security concerns in Rio before coming high-profile events